It is previously known that guanidine derivatives of some compounds possess antimicrobial or pesticidal properties. U.S. Pat. No. 2,289,541 describes the utilization of dodecylguanidine acetate and similar compounds as insecticides and in U.S. Pat. No. 2,867,562 states that the same compounds are particularly active against fungi on fruit trees. It is further known from British Pat. No. 1,114,155 that specific guanidated polyamines are used against pathogenic organisms. However, this British Patent relates to polyamines having only the primary amino groups, i.e. the end-groups of the polyamine, quanidated and it is furthermore characteristic of these bis-guanidine derivatives that the two guanidine groups are separated by at least 12 carbon and nitrogen atoms.